1. Field of the Invention
This invention relates generally to an apparatus for use with the demolition machine for underground excavation and, more particularly, to apparatus for placing support plates against the roof of an underground excavation for subsequent use with rock bolts.
2. Description of the Background
When performing underground construction, such as tunnel building or mining, it is frequently required to support the overhead portion or roof of the tunnel. Although in the past timbering was one conventional approach to achieve roof supporting, recently a new technique known as rock bolting or roof bolting has become popular. In accordance with this technique bolts that are around 3/4-1 inch in diameter and from 4-8 feet long are embedded in the tunnel roof to prevent cave-ins. Typically attached to one threaded end of the rock bolt is a bearing plate or support plate that is retained by a nut threaded to the rod.
The support plates generally are placed transversely relative to the width of the gallery or underground excavation and the plates anchored to the roof by the rock bolts that are installed by drilling holes through the plates and then placing the rock bolts or anchor rods through the plates into the roof. In the placement of these support plates, the operations known heretofore involved the positioning of the plate and pressing it to the overhead portion of the tunnel with pistons and then boring holes through holes in the plates into the roof or overhead portion of the underground excavation. Once the holes are bored in the roof then the rock bolts, in the form of threaded rods, are introduced and locked in the holes. In some cases the end of the bolt is first split then expanded by a wedge in the hole. The other end of the bolt or anchor is threaded and after the support plate is placed over the threaded end a nut is tightened thereon, thereby holding the support plate firmly in place. One other approach is to inject a resin into the hole to lock the rock bolt therein.
Among the several disadvantages that are inherent in the known approach to using support plates and rock bolts as described above are the great deal of time that is required to align the anchor rods and the holes in the roof and also to align a suitable device for introducing the synthetic resin into the holes so that the anchor rods may be firmly held in the roof. There is also an appreciable length of time required to align the anchor rods with the through holes formed in the support plate. Perhaps most important, however, is the disadvantage in the known procedure in that the roof is not yet supported during placement of the anchors and plates and, thus, working in the area where the rock bolts and support plates are being installed is highly dangerous.